How to Calculate Pooled Estimated Variation

Sum of Squares

• 1

  Find the mean for a group by summing all values of that group and dividing by the number of values.

• 2

  Subtract the mean from each value of the group. Call this new set of data A.

• 3

  Square each value in the dataset A.

• 4

  Sum all of the squared values. This is your sum of squares for that group.

• 5

  Repeat this process for all remaining groups.

Degrees of Freedom

• 6

  Count the number of values for each group.

• 7

  Sum all of these values. Call this number N.

• 8

  Subtract the number of groups from N. This is your within groups degrees of freedom. Call this value DF.

Pooled Estimated Variation

• 9

  Sum all of the sums of squares you calculated previously. Call this value SS.

• 10

  Divide SS by DF. This is your pooled estimated variation.

• 11

  Check your answer by taking its square root. This square root should be of similar size to your sample's individual standard deviations.